It took less than three months for an online coding game to transform James Johnston’s life.

Johnston, 31, was designing software for orthodontists and living in Chattanooga, Tennessee, when he landed a better-paid software engineering job in Silicon Valley at a major tech startup.

The key to this career upgrade and cross-country move? CodeFights, an online game that offers programmers the chance to improve their skills and get noticed by Silicon Valley titans like Uber and Dropbox.

Johnston told CNNMoney he discovered the game through a Facebook ad in June.

“I was kind of intrigued and thought it was a fun little activity,” he said.